Fürst Christian zu Bentheim und Steinfurt turns 100 years old today, 9 December 2023. He is doing well for his age and is spending the day with his family.
As far as I remember, he is not only the all-time oldest descendant of Frederik VIII of Denmark but also of Christian IX.

Christian IX –> Frederik VIII –> Louise (m. Schaumburg-Lippe) –> Stephanie (m. Bentheim-Steinfurt) –> Christian

He is a second cousin of the Queen of Denmark, the King of Norway and the Fürst of Waldeck-Pyrmont.

https://bnn.network/world/germany/prince-christian-of-bentheim-steinfurt-a-century-of-royal-legacy/

https://rp-online.de/nrw/staedte/rheinberg/alpen-christian-fuerst-zu-bentheim-und-steinfurt-feiert-am-9-dezember-seinen-100-geburtstag_aid-102937113